Going round in Circles..Buffering/ArcObjects/VBA

Question

I've just started learning VBA and ArcObjects, and at the moment just playing around trying to do different things. What i am trying to do is Click on a tool, and allow the user to put a point graphic on the map, but also buffer the point(marker) that has been added. I can get the point on the map, but seem to be going round in circles getting the buffer to work. Can someone give me some hints ( i don't want the exact answer just some guidance on where I am going wrong.

Code is here.

Private Sub Buffer_MouseDown(ByVal button As Long, ByVal shift As Long, ByVal x As Long, ByVal y As Long)
Dim pMxDoc As IMxDocument ' Create Object for current document
Set pMxDoc = ThisDocument ' Set object to current Document
Dim pMap As IMap ' Create object for current map
Set pMap = pMxDoc.FocusMap ' Set object to the current active map
Dim pPoint As IPoint 'Create object for point on map
Set pPoint = pMxDoc.CurrentLocation ' Set object to current location
Dim pElement As IElement ' Create object for graphic THAT IS ADDED TO THE MAP!!!!
Set pElement = New MarkerElement ' Set object to a new marker element (point graphic)
pElement.Geometry = pPoint ' Assign the geometry of the element to the Point.
Dim pGraphics As IGraphicsContainer ' Create object to hold the graphic
Set pGraphics = pMap ' Set object to current active map
pGraphics.AddElement pElement, 0 ' Set the graphic that will be added
Dim pActiveView As IActiveView ' Create object for active map display
Set pActiveView = pMxDoc.ActiveView ' Set object to the Active view
'--------------CREATE BUFFER------------------------'
 Dim pSpaRef As ISpatialReference3
 Set pSpaRef = pMap.SpatialReference
 Dim pFCBuffer As IFeatureCursorBuffer2 ' Create Object for buffer
 Set pFCBuffer = New FeatureCursorBuffer ' Set object for new buffer
 pFCBuffer.Dissolve = True
 pFCBuffer.ValueDistance = 100
 Set pFCBuffer.BufferSpatialReference = pSpaRef
 Set pFCBuffer.DataFrameSpatialReference = pSpaRef
 Set pFCBuffer.SourceSpatialReference = pSpaRef
 Set pFCBuffer.TargetSpatialReference = pSpaRef
 Dim pCGLayer As ICompositeGraphicsLayer2
 Set pCGLayer = New CompositeGraphicsLayer
 Dim pGLayer As IGraphicsLayer
 Set pGLayer = pMap.ActiveGraphicsLayer
 pFCBuffer.BufferToGraphics pGLayer
 pActiveView.PartialRefresh esriViewGraphics, pElement, Nothing ' [partial refresh of the graphics element.
 End Sub

Answer 1

Halil,

The interface you are using to create the buffers IFeatureCursorBuffer2 creates buffers for selected features. Your point that you create based upon the users button click is not a feature but a graphic which you are adding to the graphics container of the map. A Feature is essentially a row in a table or featureclass.

As you are adding your point as a graphic I assume the buffer you want to create will also end up as a graphic. Use the interface ITopologicalOperator and it's method Buffer to create a polygon then do as you did with your point, create a graphic element.

• MapMan: Duncun, i have added the following Dim pTopoOp As ITopologicalOperator2 Dim pBuffPoly As IPolygon Set pTopoOp = pPoint.GeometryType Set pBuffPoly = pTopoOp.Buffer(1000) but I get a type mismatch error on line 3, i've also tried Set pTopoOp = pElement.Geometry but get the same mismatch error. Halil
• Hornbydd: The line "Set pTopoOp = pPoint.GeometryType" should be "Set pTopoOp = pPoint"